Graphite

Graphite is a crystalline form of carbon and one of the most familiar allotropes of the element. Like diamond, it is a pure form of carbon, but its atoms are arranged in two-dimensional sheets of hexagonal lattices. The sheets are strongly covalently bonded, while the interlayer forces are weak, allowing sheets to slide over each other easily. This gives graphite its lubricity and makes it a good conductor of electricity and heat, while giving it a very high thermal stability.

Graphite occurs naturally in several forms. In geology, it is mined as natural graphite and categorized into amorphous, flake, and vein (lump) varieties, depending on crystal size and occurrence. It forms in metamorphic rocks from carbon-rich fluids and in igneous rocks in some pegmatites and hydrothermal veins. Synthetic graphite is also produced by high-temperature treatment of carbon-rich materials.

Key properties include chemical inertness at room temperature, high melting point, and anisotropic conductivity (electrical conductivity is much higher along the a-b planes than across them). It is a good lubricant in dry conditions and has a relatively low density for a carbon material.

Industrial production combines natural graphite mining and processing with the manufacture of synthetic graphite from petroleum coke or coal tar pitch. Natural graphite is refined and sized for applications, while synthetic graphite is often used for high-purity needs such as electrodes in metallurgy and lithium-ion battery anodes.

Major uses include pencils and writing, lubricants and refractory materials, crucibles and refractories in high-temperature furnaces, electrodes for aluminum smelting and electrochemical cells, and reinforced graphite composites for aerospace and automotive applications. In some nuclear reactors, specially manufactured graphite serves as a neutron moderator and reflector.

Health and environmental considerations include the potential hazards of inhaling fine graphite dust, which can cause respiratory irritation and, with chronic exposure, pneumoconiosis. Proper handling and ventilation reduce risk.